Fix tracking of float counters in Redis (#42)

* Fix the check for new counters when using floats

Signed-off-by: Justin Nuß <justin.nuss@hmmh.de>

Co-authored-by: Lukas Kämmerling <lukas.kaemmerling@hetzner-cloud.de>

Author: nussjustin-hmmh

examples/some_counter.php

@@ -17,7 +17,11 @@
 }
 $registry = new CollectorRegistry($adapter);
 
+$count = preg_match('/^[0-9]+$/', $_GET['c'])
+    ? intval($_GET['c'])
+    : floatval($_GET['c']);
+
 $counter = $registry->registerCounter('test', 'some_counter', 'it increases', ['type']);
-$counter->incBy($_GET['c'], ['blue']);
+$counter->incBy($count, ['blue']);
 
 echo "OK\n";

src/Prometheus/Storage/Redis.php

@@ -288,9 +288,9 @@ public function updateCounter(array $data): void
         $this->redis->eval(
             <<<LUA
 local result = redis.call(ARGV[1], KEYS[1], ARGV[3], ARGV[2])
-if result == tonumber(ARGV[2]) then
+local added = redis.call('sAdd', KEYS[2], KEYS[1])
+if added == 1 then
     redis.call('hMSet', KEYS[1], '__meta', ARGV[4])
-    redis.call('sAdd', KEYS[2], KEYS[1])
 end
 return result
 LUA

tests/Test/BlackBoxTest.php

@@ -64,15 +64,24 @@ public function gaugesShouldBeOverwritten(): void
 
     /**
      * @test
+     * @dataProvider countersDataProvider
+     * @param int|float $increment
      */
-    public function countersShouldIncrementAtomically(): void
+    public function countersShouldIncrementAtomically($increment): void
     {
         $start = microtime(true);
         $promises = [];
         $sum = 0;
+        $n = $increment;
         for ($i = 0; $i < 1100; $i++) {
-            $promises[] =  $this->client->getAsync('/examples/some_counter.php?c=' . $i . '&adapter=' . $this->adapter);
-            $sum += $i;
+            if (is_float($n)) {
+                $url = '/examples/some_counter.php?c=' . number_format($n, 2) . '&adapter=' . $this->adapter;
+            } else {
+                $url = '/examples/some_counter.php?c=' . $n . '&adapter=' . $this->adapter;
+            }
+            $promises[] =  $this->client->getAsync($url);
+            $sum += $n;
+            $n += $increment;
         }
 
         Promise\settle($promises)->wait();
@@ -85,6 +94,17 @@ public function countersShouldIncrementAtomically(): void
         self::assertThat($body, self::stringContains('test_some_counter{type="blue"} ' . $sum));
     }
 
+    /**
+     * @return array<int, array<float|int>>
+     */
+    public function countersDataProvider(): array
+    {
+        return [
+            [1],
+            [0.5]
+        ];
+    }
+
     /**
      * @test
      */